Mitigating audible noise in a display having an integrated touch sensor

ABSTRACT

An example method of driving a display having a touch sensor includes: generating a plurality of display frames having an alternating sequence of display and blanking periods; supplying pixel line data to the display during the display periods and sensing signals to the touch sensor during the blanking periods; and timing the blanking periods so that display frames of a first type each have a first number of the blanking periods and that display frames of a second type each have a second number of the blanking periods, the second number less than the first number.

BACKGROUND

Field of the Disclosure

Embodiments of disclosure generally relate to electronic circuits and,more particularly, to techniques for mitigating audible noise in adisplay having an integrated touch sensor.

Description of the Related Art

Input devices including proximity sensor devices (also commonly calledtouchpads or touch sensor devices) are widely used in a variety ofelectronic systems. A proximity sensor device can include a sensingregion, often demarked by a surface, in which the proximity sensordevice determines the presence, location and/or motion of one or moreinput objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computing systems (such as touch screens integrated in displaysof mobile phones). A proximity sensor can include a large number ofparallel channels for processing signals resulting from touch sensingoperations. Thus, the complexity and cost for each channel is critical.

SUMMARY

In an embodiment, a method of driving a display having a touch sensorincludes: generating a plurality of display frames having an alternatingsequence of display and blanking periods; supplying pixel line data tothe display during the display periods and sensing signals to the touchsensor during the blanking periods; and timing the blanking periods sothat display frames of a first type each have a first number of theblanking periods and that display frames of a second type each have asecond number of the blanking periods, the second number less than thefirst number.

In another embodiment, a processing system for a display having a touchsensor includes: display driver circuitry configured to generate aplurality of display frames having an alternating sequence of displayand blanking periods, and supply pixel line data to the display duringthe display periods; sensor circuitry configured to supply sensingsignals to the touch sensor during the blanking periods; and controlcircuitry configured to time the blanking periods so that display framesof a first type each have a first number of the blanking periods andthat display frames of a second type each have a second number of theblanking periods, the second number less than the first number.

In another embodiment, an input device includes: a display; a touchsensor integrated in the display; and a processing system, including:display driver circuitry configured to generate a plurality of displayframes having an alternating sequence of display and blanking periods,and supply pixel line data to the display during the display periods;sensor circuitry configured to supply sensing signals to the touchsensor during the blanking periods; and control circuitry configured totime the blanking periods so that display frames of a first type eachhave a first number of the blanking periods and that display frames of asecond type each have a second number of the blanking periods, thesecond number less than the first number.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate only someembodiments of this disclosure and are therefore not to be consideredlimiting of its scope, for the disclosure may admit to other equallyeffective embodiments.

FIG. 1 is a block diagram of an exemplary input device, according to oneembodiment described herein.

FIG. 2 is a block diagram depicting a processing system coupled to adisplay of an input device according to an embodiment.

FIG. 3 is a block diagram that depicts a display frame structureaccording to an embodiment.

FIG. 4 is a block diagram depicting a logical arrangement of displayframes generated by display driver circuitry according to an embodiment.

FIG. 5 is a block diagram illustrating a first timing scheme accordingto an embodiment.

FIG. 6 is a block diagram illustrating a second timing scheme accordingto an embodiment.

FIG. 7 is a flow diagram depicting a method of generating display framesfor a display according to an embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings should not be understood as beingdrawn to scale unless specifically noted. Also, the drawings may besimplified and details or components omitted for clarity of presentationand explanation. The drawings and discussion serve to explain principlesdiscussed below, where like designations denote like elements.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an exemplary input device 100, inaccordance with embodiments of the disclosure. The input device 100 maybe configured to provide input to an electronic system (not shown). Asused in this document, the term “electronic system” (or “electronicdevice”) broadly refers to any system capable of electronicallyprocessing information. Some non-limiting examples of electronic systemsinclude personal computers of all sizes and shapes, such as desktopcomputers, laptop computers, netbook computers, tablets, web browsers,e-book readers, and personal digital assistants (PDAs). Additionalexample electronic systems include composite input devices, such asphysical keyboards that include input device 100 and separate joysticksor key switches. Further example electronic systems include peripheralssuch as data input devices (including remote controls and mice), anddata output devices (including display screens and printers). Otherexamples include remote terminals, kiosks, and video game machines(e.g., video game consoles, portable gaming devices, and the like).Other examples include communication devices (including cellular phones,such as smart phones), and media devices (including recorders, editors,and players such as televisions, set-top boxes, music players, digitalphoto frames, and digital cameras). Additionally, the electronic systemcould be a host or a slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system, or can be physically separate from the electronicsystem. As appropriate, the input device 100 may communicate with partsof the electronic system using any one or more of the following: buses,networks, and other wired or wireless interconnections. Examplecommunication protocols include Inter-Integrated Circuit (I²C), SerialPeripheral Interface (SPI), Personal System/2 (PS/2), Universal SerialBus (USB), Bluetooth®, Radio Frequency (RF), and Infrared DataAssociation (IrDA) communication protocols.

In FIG. 1, the input device 100 is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120 using sensor electrodes 125. Example input objectsinclude fingers and styli, as shown in FIG. 1.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments, the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be on theorder of less than a millimeter, millimeters, centimeters, or more, andmay vary significantly with the type of sensing technology used and theaccuracy desired. Thus, in some embodiments, sensing input may compriseno contact with any surfaces of the input device 100, contact with aninput surface (e.g. a touch surface) of the input device 100, contactwith an input surface of the input device 100 coupled with some amountof applied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes 125 reside, by face sheets appliedover the sensor electrodes 125 or any casings, etc. In some embodiments,the sensing region 120 has a rectangular shape when projected onto aninput surface of the input device 100.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements fordetecting user input. As several non-limiting examples, the input device100 may use capacitive, elastive, resistive, inductive, magnetic,acoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some capacitive implementations of the input device 100, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes 125.Some capacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self-capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes 125 and an input object. In variousembodiments, an input object near the sensor electrodes 125 alters theelectric field near the sensor electrodes 125, thus changing themeasured capacitive coupling. In one implementation, an absolutecapacitance sensing method operates by modulating sensor electrodes 125with respect to a reference voltage (e.g. system ground), and bydetecting the capacitive coupling between the sensor electrodes 125 andinput objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes 125. In various embodiments, an inputobject near the sensor electrodes 125 alters the electric field betweenthe sensor electrodes 125, thus changing the measured capacitivecoupling. In one implementation, a transcapacitive sensing methodoperates by detecting the capacitive coupling between one or moretransmitter sensor electrodes (also “transmitter electrodes” or“transmitters”) and one or more receiver sensor electrodes (also“receiver electrodes” or “receivers”). Transmitter sensor electrodes maybe electrically modulated relative to a reference voltage (e.g., systemground) to transmit transmitter signals. Receiver sensor electrodes maybe held substantially constant relative to the reference voltage tofacilitate receipt of resulting signals. A resulting signal may compriseeffect(s) corresponding to one or more transmitter signals, and/or toone or more sources of environmental interference (e.g. otherelectromagnetic signals). Sensor electrodes 125 may be dedicatedtransmitters or receivers, or may be configured to both transmit andreceive.

In FIG. 1, a processing system 110 is shown as part of the input device100. The processing system 110 is configured to operate the hardware ofthe input device 100 to detect input in the sensing region 120. Theprocessing system 110 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. Forexample, a processing system for a mutual capacitance sensor device maycomprise transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes). In some embodiments,the processing system 110 also comprises electronically-readableinstructions, such as firmware code, software code, and/or the like. Insome embodiments, components composing the processing system 110 arelocated together, such as near sensing element(s) of the input device100. In other embodiments, components of processing system 110 arephysically separate with one or more components close to sensingelement(s) of input device 100, and one or more components elsewhere.For example, the input device 100 may be a peripheral coupled to adesktop computer, and the processing system 110 may comprise softwareconfigured to run on a central processing unit of the desktop computerand one or more ICs (perhaps with associated firmware) separate from thecentral processing unit. As another example, the input device 100 may bephysically integrated in a phone, and the processing system 110 maycomprise circuits and firmware that are part of a main processor of thephone. In some embodiments, the processing system 110 is dedicated toimplementing the input device 100. In other embodiments, the processingsystem 110 also performs other functions, such as operating displayscreens, driving haptic actuators, etc.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes 125 and display screens, data processing modules forprocessing data such as sensor signals and positional information, andreporting modules for reporting information. Further example modulesinclude sensor operation modules configured to operate sensingelement(s) to detect input, identification modules configured toidentify gestures such as mode changing gestures, and mode changingmodules for changing operation modes.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as graphical user interface (GUI) actions such as cursormovement, selection, menu navigation, and other functions. In someembodiments, the processing system 110 provides information about theinput (or lack of input) to some part of the electronic system (e.g. toa central processing system of the electronic system that is separatefrom the processing system 110, if such a separate central processingsystem exists). In some embodiments, some part of the electronic systemprocesses information received from the processing system 110 to act onuser input, such as to facilitate a full range of actions, includingmode changing actions and GUI actions.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 110 may digitizeanalog electrical signals obtained from the sensor electrodes 125. Asanother example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1 shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 100 may be implemented with no other inputcomponents.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen. For example, the input device 100 maycomprise substantially transparent sensor electrodes 125 overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system. The display screen may be any type of dynamic displaycapable of displaying a visual interface to a user, and may include anytype of light emitting diode (LED), organic LED (OLED), cathode ray tube(CRT), liquid crystal display (LCD), plasma, electroluminescence (EL),or other display technology. The input device 100 and the display screenmay share physical elements. For example, some embodiments may utilizesome of the same electrical components for displaying and sensing. Asanother example, the display screen may be operated in part or in totalby the processing system 110.

It should be understood that while many embodiments of the disclosureare described in the context of a fully functioning apparatus, themechanisms of the present disclosure are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present disclosure may be implemented anddistributed as a software program on information bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present disclosure apply equally regardless of the particular typeof medium used to carry out the distribution. Examples ofnon-transitory, electronically readable media include various discs,memory sticks, memory cards, memory modules, and the like.Electronically readable media may be based on flash, optical, magnetic,holographic, or any other storage technology.

FIG. 2 is a block diagram depicting the processing system 110 coupled toa display 212 of the input device 100 according to an embodiment. Thedisplay 212 includes a display cell 214. The display cell 214 includes apixel array 216 and touch electrodes 218. The pixel array 216 includesrows and columns of pixels. Each pixel includes a light-emitting elementand associated driving circuitry. For example, the pixels can beimplemented using liquid crystal display (LCD), light-emitting diode(LED), organic LED (OLED), and the like technology. The drivingcircuitry of the pixel array 216 can be implemented using thin-filmtransistor (TFT) circuits.

The touch electrodes 218 comprise conductive elements disposed in thedisplay cell 214. The touch electrodes 218 can be dedicated for thefunction of capacitive touch sensing or can function for both capacitivetouch sensing and display updating. For example, in an LCD display, thetouch electrodes 218 can be segments of a common electrode (e.g.,segments of a VCOM electrode). In an LED display, the touch electrodes218 can be anodes or cathodes of LEDs in the pixel array 216. In stillother examples, the touch electrodes 218 can be source lines, gatelines, or other conductive lines disposed in the display cell 214. Thetouch electrodes 218 can be disposed on a substrate within one or morelayers. The touch electrodes 218 can be arranged in various patterns,such as bars, bars and stripes, matrix patterns, or the like. In anembodiment, the display 212 also includes additional touch electrodes220 dispose outside of the display cell 214 (e.g., on the display cell214 or on some other substrate or layer above or below the display cell214). For example, the touch electrodes 220 can be disposed on a colorfilter substrate above the display cell 214, on a cover substrate abovethe display cell 214, or the like. The touch electrodes 220 can form apattern with the touch electrodes 218 (e.g., a bars and stripespattern). In an embodiment, the touch electrodes 218 and the touchelectrodes 220 are used as transmitters and receivers or receivers andtransmitters, respectively.

The processing system 110 includes sensor circuitry 202, controlcircuits 210, display driver circuitry 204, and processing circuits 222.The sensor circuitry 202 includes analog or both analog and digitalcircuits configured to operate the touch electrodes 218, 220 to performcapacitive sensing of input objects touching or in proximity with thedisplay 212. The sensor circuitry 202 can include charge measurementcircuits (e.g., charge integrators, current conveyors, etc.),demodulators, filters, analog-to-digital converters (ADCs), and thelike. The sensor circuitry 202 operators to generate resulting signalsfrom the touch electrodes 218 or the touch electrodes 220 that areindicative of changes in capacitance due to input object(s). The sensorcircuitry 202 can perform absolute capacitive sensing, transcapacitivesensing, or both.

The display driver circuitry 204 includes source drivers 206. The sourcedrivers 206 are coupled to source lines in the display cell 214 fordriving data to the pixel array 216, where the data includes image(s) tobe displayed. The source drivers 206 can be coupled to the source linesin the display cell 214 through demultiplexer circuits, which can bepart of the display driver circuitry 204 or part of the display cell 214(e.g., formed using TFT layers). The source drivers 206 provide data tothe pixel array 216 one line at a time. Gate selection circuitry 208 iscoupled to gate lines in the display cell 214 for selecting differentlines (e.g., different rows) to receive data from the source drivers206. In an embodiment, the gate selection circuitry 208 is integrated inthe display 212 (e.g., using TFT layers of the display cell 212).Alternatively, the gate selection circuitry 208 can be part of thedisplay driver circuitry 204.

The control circuits 210 are coupled to both the sensor circuitry 202and the display driver circuitry 204. The control circuits 210 caninclude registers, multiplexers, combinatorial logic, state machine(s),or the like. The control circuits 210 operate to control various aspectsof the sensor circuitry 202 and the display driver circuitry 204, asdiscussed further herein. The processing circuits 222 includeprocessor(s), memory, input/output (IO) circuits, and the like. Theprocessing circuits 222 can be coupled to the sensor circuitry 202, thecontrol circuits 210, and the display driver circuitry 204. Theprocessing circuits 222 can provide commands to the control circuit 210to set the parameters of the sensor circuitry 202 and the display drivercircuitry 204. The processing circuits 222 can receive resulting signalsfrom the sensor circuitry 202. The processing circuits 222 can provideimage data to the display driver circuitry 204 to be displayed on thedisplay 212. The processing circuits 222 can include a graphicsprocessing unit (GPU) or can receive image data from an external GPU orthe like. In another embodiment, the display driver circuitry 204 canreceive image data directly from an external GPU or the like (as opposedto receiving the image data from the processing circuits 222). Theprocessing circuits 222 can include software, firmware, hardware, or acombination thereof to perform various functions, such as providingcommands to the control circuits 210, processing resulting signals fromthe sensor circuitry 202 to determine changes in capacitance and objectdetection, and the like.

FIG. 3 is a block diagram that depicts a display frame structure 300according to an embodiment. The display driver circuitry 204 receivesdisplay data and generates a sequence of display frames 301 as output.The display frames 301 can be output at a constant or substantiallyconstant frame rate (e.g., 60 frames per second (FPS)). Each displayframe 301 includes an alternating sequence of blanking periods anddisplay periods (DPs). The blanking periods are referred to herein aslong horizontal blanking periods or “LHBs”. As shown in FIG. 3, adisplay frame 301 includes LHBs 302 and DPs 306 in an alternatingsequence. The beginning and the end of the display frame 301 can includeother periods (e.g., other period 304 and other period 308) insertedbetween an LHB 302 and a DP 306. The other periods 304, 308 can includea back porch period, a front porch period, dummy lines, and the like.

Each DP 306 includes a plurality of lines 310. Each line 310 includespixel data for updating a row of pixels in the pixel array 216. Ingeneral, each DP 306 can include the same number of lines. In anembodiment, a first DP 306 in the display frame 301 can include adifferent number of lines than each other DP 306 (which include the samenumber of lines). Thus, the width (duration) of the DP 306 is measuredin terms of a number of lines 310. Each line 310 includes a durationreferred to as a line time.

Each LHB 302 also has a width of a plurality of lines (e.g., an integermultiple of the line time). Each LHB 302 includes a touch period 312.The touch period 312 can have a width that is the same as or less thanthe width of the LHB 302. During a touch period 312, the sensorcircuitry 202 drives the touch electrodes with sensing signals forcapacitive sensing. In an embodiment, the sensor circuitry 202 operatesusing a sequence of discrete touch bursts (also referred to as“bursts”). The sensor circuitry 202 dries the touch electrodes withsensing signals during each touch burst and does not drive the touchelectrodes with sensing signals between touch bursts. The touch period312 can include a certain number of touch bursts.

The input data to the display driver circuitry 204 is also formattedinto frames 318. The duration of each display frame 301 can be the sameas the duration of each frame 318 of the input data. Each frame 318 ofthe input data includes groups of input lines 314. A combined width 316of an LHB 302, optionally the other period 304, and the DP 306 is equalto a width of an input line group 314. For example, a group of inputlines 314 can include 50 lines. The data for the 50 lines is compressedinto a DP 306 of the display frame 301. The line time is shortened tomake room for the LHB 302 and optionally the other period 304. Within aninput frame 318, each group of lines 314 can include the same number oflines. Optionally, one of the groups of input lines 314 (e.g., a firstgroup) can include more lines than each other group of input lines 314(which include the same number of lines).

FIG. 4 is a block diagram depicting a logical arrangement of displayframes generated by the display driver circuitry 204 according to anembodiment. In some cases, a sequence of LHBs 302 in the display framesoutput by the display driver circuitry 204 can cause an audible noise tobe emitted from the input device 100. In embodiments described herein,the sequence of LHBs 302 is altered in at least one of two ways tomitigate audible noise. In a first timing scheme, the number and widthof LHBs 302 is varied from one frame to the next. In a second timingscheme, the position of the LHBs 302 within each display frame 301 isvaried from one frame to the next. In some embodiments, both the firstand second timing schemes can be employed to mitigate audible noise. Thetiming schemes spread the spectrum of any generated noise so as tobecome inaudible or substantially inaudible.

In the first timing scheme, the display frames 301 are divided intoframe sequences 402. Each frame sequence 402 includes a plurality ofdisplay frames of different types. In general, a frame sequence 402 caninclude N frame types resulting in N different types of frames 404 ₁through 404 _(N) (where N is an integer greater than one). Each type ofdisplay frame 404 includes a sequence of display periods 306, a sequenceof blanking periods (e.g., LHBs 302), and a sequence of sensing bursts406. The blanking periods 302 are interleaved with the display periods306, as shown in FIG. 3 and described above. The sensing bursts 406occur within the blanking periods 302, as shown in FIG. 3 and describedabove. Each type of display frame 404 has a unique number 408 ofblanking periods 302 and a unique width 409 of the blanking periods 302.That is, the number 408 and the width 409 of the blanking periods 302varies across the types of display frames 404 ₁ . . . 404 _(N). Varyingthe number and width of the blanking periods 302 implements the firsttype of timing scheme discussed above. In an embodiment, the totalnumber of sensing bursts 406 is constant from frame-to-frame. Thus, anumber 412 of sensing bursts per touch period changes across the typesof frames 404 ₁ . . . 404 _(N) in the first timing scheme.

In an embodiment, the number 408 of the blanking periods 302 can haveone of a plurality of discrete values. Likewise, the width 409 of theblanking periods 302 can have one of a plurality of discrete widths. Inan embodiment, the plurality of discrete values for each of the number408 and the width 409 of the blanking periods 302 either increases ordecreases monotonically. Table 1 illustrates an example configuration ofthe first timing scheme:

TABLE 1 Display Frame # in LHB period Number of LHBs in Frame Sequence(time) one display frame 1 X Y 2 2*X Y/2 3 3*X Y/3 . . . . . . . . . NN*X us Ceiling(Y/N)

In Table 1, the number 408 of the blanking periods 302 decreasesmonotonically, while the width 409 of the blanking periods 302 increasesmonotonically, across the display frame types 404 ₁ . . . 404 _(N). Inanother embodiment, the number 408 of the blanking periods 302 canincrease monotonically, while the width 409 of the blanking periods 302can decrease monotonically. Table 2 illustrates another exampleconfiguration of the first timing scheme:

TABLE 2 Display Frame # in LHB period Number of LHBs in Frame Sequence(time) one display frame 1 X Y 2 2*X Y/2 3 4*X Y/4 . . . . . . . . . N(2*N)*X Ceiling(Y/(2*N))

The spectrum of audible noise has odd harmonics of a fundamentalfrequency matching a rate of the blanking periods 302. So, in anembodiment of the first timing scheme, the number 408 of blankingperiods 302 is increases or decreased monotonically by even multiples.

In the second timing scheme, a phase 410 of the blanking periods 302 ischanged from one frame to the next. As discussed above, a frame includesa plurality of lines corresponding to the rows of the pixel array 216.Each line includes an index (e.g., 1^(st) line, 2^(nd) line, and so on).The phase 410 of the blanking periods 302 can be changed by adjustingthe line index prior to and after the first blanking period 302 in thesequence. Alternatively, only one of the line index prior to or afterthe first blanking period 302 is adjusted (i.e., the first blankingperiod has a different width than each other blanking period in thesequence). The phase can shift left or right in time monotonically fromone display frame to the next. Alternatively, rather than shifting thephase frame-to-frame, the phase can be shifted across the same frametypes. For example, the type one frame in one frame sequence can haveone phase and the type one frame in the next frame sequence can have adifferent phase.

FIG. 5 is a block diagram illustrating a first timing scheme 500according to an embodiment. In the example, the first timing scheme 500is for two different frame types per frame sequence. For frame type 1,each LHB 302 includes a sequence of bursts 502. For frame type 2, eachLHB 302 is longer than each LHB 302 in frame type 1. Moreover, the frametype 2 includes less LHBs 302 per frame. In the frame type 2, each LHB302 includes two sequences of bursts 502 (e.g., the number of bursts perLHB 302 is increased with respect to the frame type 1). The example ofFIG. 5 can be extended for any number of frame types per frame sequence.

FIG. 6 is a block diagram illustrating a second timing scheme 600according to an embodiment. In the example, the second timing scheme6700 is for three different phases for the frame type 1. A firstinstance of the frame type 1 in the frame sequence has a first phase P1.A second instance of the frame type 1 in the frame sequence has a secondphase P2. A third instance of the frame type 1 in the frame sequence hasa third phase P3. The example of FIG. 6 can be extended for any numberof phases for the frame type 1. After the last phase (e.g., P3), thenext instance of frame type 1 has the phase P1 (e.g., P1, P2, P3, P1,P2, P3, etc.). Alternatively, the phase adjustment can snake (e.g., P1,P2, P3, P2, P1, P2, P3, etc.). While the example of FIG. 6 showschanging phase for one frame type, the same scheme can be employed foreach frame type. In another embodiment, rather than varying the phaseacross instances of the same frame type, the phase can be varied fromframe-to-frame (regardless of frame type).

FIG. 7 is a flow diagram depicting a method 700 of generating displayframes for a display according to an embodiment. The blocks in themethod 700 do not occur in sequential order, but are rather implementedconcurrently by the processing system 110. The method 700 includes ablock 702, where the display driver circuitry 204 generates a pluralityof display frames from input display data. The display frames include analternating sequence of blanking periods and display periods. In somecases, other periods can be inserted between certain pairs of theblanking periods and the display periods, as shown in the example ofFIG. 3.

The method 700 includes a block 704, where the display driver circuitry204 supplies pixel line data to the display during the display periodsand the sensor circuitry 202 provides sensing signals to the touchelectrodes (collectively referred to as a touch sensor) during theblanking periods.

The method 700 includes a block 706, where the control circuits 210 timethe blanking periods according to the first timing scheme. The controlcircuits 210 control both the number of blanking periods per displayframe and the width (duration) of the blanking periods across frames.The control circuits 210 can receive a schedule for the first timingscheme from the processing circuits 222 (e.g., a schedule of Table 1above, a schedule of Table 2 above, etc.).

The method 700 can optionally include a block 708, where the controlcircuits 210 time the blanking periods according to the second timingscheme. The control circuits 210 control the phase of the blankingperiod sequence from frame-to-frame or instance-to-instance of eachframe type. The control circuits 210 can receive a schedule for thesecond timing scheme from the processing circuits 222.

The embodiments and examples set forth herein were presented to explainthe embodiments in accordance with the present technology and itsparticular application and to thereby enable those skilled in the art tomake and use the disclosure. However, those skilled in the art willrecognize that the foregoing description and examples have beenpresented for the purposes of illustration and example only. Thedescription as set forth is not intended to be exhaustive or to limitthe disclosure to the precise form disclosed.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow.

I claim:
 1. A method of driving a display having a touch sensor,comprising: generating a plurality of display frames having analternating sequence of display periods and blanking periods, whereinthe plurality of display frames comprises display frames of a first typeand display frames of a second type; supplying pixel line data to thedisplay during the display periods and sensing signals to the touchsensor during the blanking periods; and timing the blanking periods sothat the display frames of the first type have a first number ofblanking periods and that the display frames of the second type have asecond number of blanking periods, wherein the second number less thanthe first number, and wherein the blanking periods in the display framesof the first type have a first width and the blanking periods in thedisplay frames of the second type have a second width, the first widthand the second width correspond to a sequential ordering of the displayframes of the first type and the display frames of the second type, andthe first number and the second number are inverse proportional to thesequential ordering.
 2. The method of claim 1, wherein a first durationof each blanking period in the display frames of the first type is lessthan a second duration of each blanking period in the display frames ofthe second type.
 3. The method of claim 2, wherein a ratio of the secondduration to the first duration is an integer greater than or equal totwo.
 4. The method of claim 1, wherein a number of the display periodsin each display frame of the first type is the same as a number of thedisplay periods in each display frame of the second type.
 5. The methodof claim 1, wherein the step of supplying the sensing signals to thetouch sensor during the blanking periods comprises generating discretesensing bursts, and wherein the method further comprises: timing thesensing bursts so that a first number of the sensing bursts occur withineach blanking period in the display frames of the first type and asecond number of the sensing bursts occur within each blanking period inthe display frames of the second type, and wherein the first number ofsensing bursts is less than the second number of sensing bursts.
 6. Themethod of claim 5, wherein a total number of the sensing bursts in eachdisplay frame of the first type is the same as a total number of thesensing bursts in each display frame of the second type.
 7. The methodof claim 1, wherein the plurality of display frames is a repeating framesequence that includes a display frame of the first type followed by adisplay frame of the second type.
 8. The method of claim 7, where therepeating frame sequence includes a first frame sequence followed by asecond frame sequence, and wherein the method further comprises:changing a phase of the blanking periods in the display frames of thefirst type between the first frame sequence and the second framesequence.
 9. The method of claim 8, further comprising: changing a phaseof the blanking periods in the display frames of the second type betweenthe first frame sequence and the second frame sequence.
 10. The methodof claim 1, further comprising: changing a phase of the blanking periodsin the plurality of display frames from one display frame to a nextdisplay frame.
 11. A processing system for a display having a touchsensor, comprising: display driver circuitry configured to generate aplurality of display frames having an alternating sequence of displayperiods and blanking periods, and supply pixel line data to the displayduring the display periods, wherein the plurality of display framescomprises display frames of a first type and display frames of a secondtype; sensor circuitry configured to supply sensing signals to the touchsensor during the blanking periods; and control circuitry configured totime the blanking periods so that the display frames of the first typehave a first number of periods and that the display frames of the secondtype have a second number of periods, wherein the second number is lessthan the first number, and wherein the blanking periods in the displayframes of the first type have a first width and the blanking periods inthe display frames of the second type of a second width, the first widthand the second width correspond to a sequential ordering of the displayframes of the first type and the display frames of the second type, andthe first number and the second number are inverse proportional to thesequential ordering.
 12. The processing system of claim 11, wherein afirst duration of each blanking period in the display frames of thefirst type is less than a second duration of each blanking period in thedisplay frames of the second type.
 13. The processing system of claim12, wherein a ratio of the second duration to the first duration is aninteger greater than or equal to two.
 14. The processing system of claim11, wherein a number of the display periods in each display frame of thefirst type is the same as a number of the display periods in eachdisplay frame of the second type.
 15. The processing system of claim 11,wherein the sensor circuitry is configured to supply the sensing signalsto the touch sensor during the blanking periods by generating discretesensing bursts, and wherein the control circuitry is configured to: timethe sensing bursts so that a first number of the sensing bursts occurwithin each blanking period in the display frames of the first type anda second number of the sensing bursts occur within each blanking periodin the display frames of the second type, and wherein the first numberof sensing bursts is less than the second number of sensing bursts. 16.The processing system of claim 15, wherein a total number of the sensingbursts in each display frame of the first type is the same as a totalnumber of the sensing bursts in each display frame of the second type.17. The processing system of claim 11, wherein the plurality of displayframes is a repeating frame sequence that includes a display frame ofthe first type followed by a display frame of the second type.
 18. Theprocessing system of claim 17, where the repeating frame sequenceincludes a first frame sequence followed by a second frame sequence, andwherein the control circuitry are configured to: change a phase of theblanking periods in the display frames of the first type between thefirst frame sequence and the second frame sequence.
 19. The processingsystem of claim 18, wherein the control circuitry are configured to:change a phase of the blanking periods in the display frames of thesecond type between the first frame sequence and the second framesequence.
 20. An input device, comprising: a display; a touch sensorintegrated in the display; and a processing system, including: displaydriver circuitry configured to generate a plurality of display frameshaving an alternating sequence of display periods and blanking periods,and supply pixel line data to the display during the display periods,wherein the plurality of display frames comprises display frames of afirst type and display frames of a second type; sensor circuitryconfigured to supply sensing signals to the touch sensor during theblanking periods; and control circuitry configured to time the blankingperiods so that the display frames of the first type have a first numberof blanking periods and that the display frames of the second type havea second number of blanking periods, wherein the second number is lessthan the first number, and wherein the blanking periods of the displayframes of the first type have a first width and the blanking periods ofthe display frames of the second type of a second width, the first widthand the second width correspond to a sequential ordering of the displayframes of the first type and the display frames of the second type, andthe first number and the second number are inverse proportional to thesequential ordering.
 21. The method of claim 1, further comprisingtiming the blanking periods so that the display frames of the first typehave at least one of a first display period duration parameter, and afirst phase parameter, and the display frames of the second type have atleast one of a second duration parameter and a second phase parameter.22. The method of claim 21, wherein the first duration parameter differsfrom the second duration parameter, and wherein the first phaseparameter differs from the second phase parameter.
 23. The processingsystem of claim 11, wherein the control circuitry is configured to timethe blanking periods so that the display frames of the first type haveat least one of a first display period duration parameter, and a firstphase parameter, and the display frames of the second type have at leastone of a second duration parameter and a second phase parameter.
 24. Theprocessing system of claim 23, wherein the first duration parameterdiffers from the second duration parameter, and wherein the first phaseparameter differs from the second phase parameter.
 25. The input deviceof claim 20, wherein a first duration of each blanking period in thedisplay frames of the first type is less than a second duration of eachblanking period in the display frames of the second type.
 26. The inputdevice of claim 20, wherein a number of the display periods in eachdisplay frame of the first type is the same as a number of the displayperiods in each display frame of the second type.
 27. The input deviceof claim 20, wherein the sensor circuitry is configured to supply thesensing signals to the touch sensor during the blanking periods bygenerating discrete sensing bursts, and wherein the control circuitry isconfigured to: time the sensing bursts so that a first number of thesensing bursts occur within each blanking period in the display framesof the first type and a second number of the sensing bursts occur withineach blanking period in the display frames of the second type, andwherein the first number of sensing bursts is less than the secondnumber of sensing bursts.
 28. The input device of claim 20, wherein theplurality of display frames is a repeating frame sequence that includesa display frame of the first type followed by a display frame of thesecond type, and wherein the method further comprises at least one of:changing a phase of the blanking periods in the display frames of thefirst type between the first frame sequence and the second framesequence; and changing a phase of the blanking periods in the displayframes of the second type between the first frame sequence and thesecond frame sequence.